Microsoft today announced success in creating a single Windows RT operating system release that supports multiple system-on-chip platforms.

Windows RT is the Windows 8 OS version that runs on ARM processors, which will be the basis for a new line of low-power-consumption tablet and PC devices that are expected to appear on the market as early as October 26. Three chipmakers have created processors based on ARM Holdings' circuit designs: Nvidia, Texas Instruments and Qualcomm. Microsoft has long collaborated with ARM Holdings in a 13-year partnership, as well as with associated ARM chipmakers. However, those collaborations mostly have focused on Windows Embedded and Windows Mobile/Windows Phone products, and not so much on tablets running ARM.

Microsoft faced some new territory with Window RT. Expectations early on were that its engineers would have to create multiple versions of Windows RT to address multiple hardware configurations and form factors. However, Microsoft appears to have created one Windows RT binary to rule them all.

"We have achieved our goal of one Windows binary for all Windows RT SoC platforms from NVIDIA, Qualcomm, and Texas Instruments, each of which has developed innovative ARM CPUs that form the basis of a complete system," stated Mike Angiulo, vice president of Microsoft's ecosystem and planning team, in a "building Windows 8" blog post.

Angiulo added that "Windows RT shares significant code with Windows 8," although he didn't provide a percentage. Unlike Windows 8 for x86/x64 systems, Windows RT will only be available preinstalled on devices. Users will be able to update their Windows RT OSes, according to Angiulo.

"Over the useful lifetime of the PC, the provided software will be serviced and improved," he wrote.

Partner Limitations
Microsoft's original equipment manufacturing (OEM) partners haven't all seemed too happy as Microsoft asserted control over Windows 8 integration. According to a report by Bloomberg, Microsoft limited the companies building Windows 8 tablets such that they could only work with just a single chip-builder partner. That same limitation on working with a single chipmaker applied when building Windows 8 notebooks, according to the Bloomberg account, which cited "people with knowledge of the plan."

J.T. Wang, chairman of computer build Acer, said during the last Computex trade show that this limitation by Microsoft was "troublesome" for both PC builders and chipmakers. More recently, Wang was reported as saying that Acer is seeking clarification on Microsoft's decision to build its own Window 8-based Surface tablet. That move by Microsoft has shocked some of its partners, as Microsoft will compete with OEM builders of Windows 8 tablets.

Asus, Dell, Lenovo and Samsung are the four computer makers mentioned by Angiulo as planning to roll out Windows RT-based devices. Other OEMs, such as Acer, have described plans to build Windows 8 machines, but they didn't get described by him.

Microsoft may be planning to broaden OEM participation in January, if a report in the China Times is correct, as reported by The Verge. Microsoft apparently controls which partners get to build Windows 8 devices first, and it then may opt to open up the ecosystem to other OEMs.

Hewlett-Packard decided to concentrate on building an x86-based Windows 8 tablets and has been considering building devices based on the ARM platform, according to a June PCMag.com story. Mobile device maker HTC was described as being shut out by Microsoft from building Windows 8 devices because of low sales or inexperience in making tablets, according to a June Bloomberg story. That's the explanation, although HTC does makes Android-based tablets. The first x86-based Windows 8 machines are expected to be released in January.

Windows RT Varieties
Windows RT will support both tablet and PC form factors, according to Angiulo. Some will have keyboards and a new touchpad that can interpret Windows 8 touch gestures. Other devices may have near-field communications capabilities, in which two adjacent devices can wirelessly share "photos, URLs, map directions, and anything else that our software partners have designed into their Windows apps," Angiulo explained.

Angiulo talked a little about application support for Windows RT devices. He claimed that more than 90 percent of the applications in the Windows Store support Windows RT. Microsoft built more than 1,500 pieces of the "Windows RT reference systems" to help software and hardware vendors get ready for Windows RT, he added.

Windows RT devices will have some differences compared with their x86/x64 Windows 8 cousins, as described in February by Steven Sinofsky, president of the Windows Division. Windows RT devices won't run x86/x64 apps. It won't be possible to carry out virtualization on Windows RT devices because virtualization consumes too much power.

Microsoft will provide Office 2013 on Windows RT devices, running on the desktop side. It's rumored that this version of Office will lack some features found in the flagship x86/x64-based Office 2013, such as support for macros and Visual Basic for Applications, as well as third-party add-in support.